Chapter 6 Flashcards
What are schedules of reinforcement?
-Rules that determine which instrumental response is followed by the reinforcer
–these schedules or rules are important as they determine the rate, pattern and persistence of instrumental behaviour
-Schedules determine choices organisms make among differing response alternatives
-Influences how instrumental response learned/maintained by reinforcement
-Schedule effects are highly relevant to motivation of behavior (hard-working or lazy depends less on personality than on the schedule of reinforcement)
What are the different Schedule types?
-Fixed-ratio,
-Variable ratio,
-Fixed interval and variable interval,
-Concurrent and concurrent-chain
*mechanisms of choice assessed typically by concurrent and concurrent-chain schedules
What is the process of Schedules of Reinforcement?
-Occurrence is followed by the reinforcer:
–in a given schedule, reinforcer delivery can depend on: presence of certain stimuli, passage of time, number of responses, etc.
-Schedules of reinforcement involving similar response-reinforcer relations produce highly predictable patterns of behaviour, though the Rate of responding can differ
What is Self-Control’s role?
-involved in selection of modest short-term gains vs. larger longer-term gains
What are Ratio Schedules?
-Ratio Schedule: reinforcement depends only on number of responses subject has to perform; reinforcer delivered each time the set, required number of responses is reached
-Continuous Reinforcement (CRF): each and every response results in delivery of reinforcer; often part of contingency management programs for drug addiction rehab centers (clean urine = voucher)
-Partial/intermittent reinforcement: responding reinforced only sometimes (enter correct PIN for ATM get cash BUT other times may get ISF notice or ATM out of order)
What is Fixed-Ratio Schedule and its components?
-Fixed-Ratio Schedule: reinforcer earned at the specific, predictable, response instance in a sequence of responses (10 responses/reinforcer = FR 10)
-Cumulative Record: total number of responses that occurred up to particular point in time or within a specified interval; complete visual record of when and frequency of subject response during a session
-Post-Reinforcement Pause: zero rate of responding that typically occurs just after reinforcement on fixed ratio; controlled by upcoming ratio requirement (number of responses); should be called pre-ratio pause (see an intimidating task ahead and you will pause)
-Ratio Run: after post-reinforcement pause, this is the high and steady rate of responding (number of responses is concern not timing) that completes each ratio requirement
-Ratio Strain: if ratio requirement is suddenly increased, animal likely to pause periodically before completion of ratio requirement
What is Variable Ratio?
-Variable-Ratio Schedule: unpredictable amount of effort, number of responses, required to earn reinforcement
− different number of responses required to obtain successive reinforcers
− predictable pauses in the rate of responding are less likely with VR than FR schedules
Are FR and VR responding rates similar or different?
-FR and VR responding rates are similar
− provided similar numbers of responses are required
− but generally, FR responses have a pause-run distribution while VR schedule
have a pattern of steady responding
− predictable pauses in the rate of responding are less likely with VR than FR schedules
What is Fixed Interval Schedule?
-Interval schedules: response is reinforced ONLY after a particular amount of time has passed
-Fixed-Interval Schedule: amount of time that must pass before a response is reinforced (constant from one trial to the next); (e.g., pigeons only reinforced if peck after 4 minutes so pigeon learns to wait until the end of the interval before increasing response rate toward end of each FI = fixed interval scallop)
-Seen in acceleration in cumulative record toward end of each fixed interval
-Addition of timing cue increases duration of post-reinforcement pause but shifts responding time closer to the end of the FI cycle
− Note, FI schedule determines when the reinforcer becomes available not when it is delivered; subject still must make the instrumental response
− A restriction on how long a reinforcer remains available is called limited hold
What is Variable Interval Schedule?
-Variable Interval Schedule: time required to set-up reinforcer, is unpredictable, varies from one trial to next (unlike FI)
–e.g., reinforcement food pellet after 1 minute; second pellet at the 3 minute mark; then after
2 more minutes the next food pellet is available; = a 2 minute set-up time for the reinforcer
-Subject has to respond to obtain the set-up reinforcer with unpredictable set-up time
-VI schedules maintain steady and stable rates of responding without regular pauses (unlike in FR)
What are the similarities of Ratio and Interval schedules?
- FR and FI schedules both have
− post-reinforcement pause after each reinforcer - FR and FI schedules both produce
− high rates of responding just before next reinforcer delivery - VR (variable ratio, number of responses) and VI (time required) schedules both,
− steady rates of responding without predictable pauses - BUT VR and V1 motivate behavior differently
− VR induced a higher rate of responses - VR schedule motivates most vigorous instrumental behavior
− due to short inter-response times (IRT) or relationship between response rates and reinforcement
− Faster the organism completes the VR response requirement the faster the
organism will be reinforced
− VI schedules favor waiting longer between responses - Frequent response before the food pellet is setup – short IRTs –will not be
- Second reason for high VR vs VI response rates
− Response rates calculated over entire experimental
session or an extended period of time; - reinforcement is consequence of responding
- Faster response schedule completed, sooner next
reinforcer obtained - Feedback function
- Is increasing, unlimited, linear function for VR, ratio
schedule; as X (response) increases so does Y
(reinforcer delivery) - Like Dr/Lawyer schedule; more clients they see more
money (reinforcer) occurs
− VI 2 minute schedule, if organism obtains each
reinforcer as it becomes available - earns max 30 rewards over 60 minutes; no more
reinforcers are possible
What are Concurrent Schedules (choice behaviour)?
- Reinforcement schedules just reviewed
− Focused on a single response and reinforcement of
that response - Concurrent Schedule
− can have more than one response option/reinforcer
− Allows continuous measurement of choices because - subject is free to change back and forth between the
response alternatives at any time (example = slot
machines in Las Vegas) - Concurrent schedule study
− Investigates mechanisms of choice
What is the measure of Choice Behaviour?
-Calculate the relative rates of responding
–relative rate of responding to LEFT key
–assume the same VI (variable time between reinforcers) schedule is same for each the left and right response keys;
* e.g., VI = 60 sec (to setup reinforcer)
-Rate of Left key response:
–(Bl/Bl+Br) = 10/10+10 = 50% Left key response rate
-Relative rate of reinforcement is the same
–reinforcers/ rewards would be equal to responses rates or the same (rL/rL+rR)
What is Matching Law?
-Relative rate of responding (Bl/Bl+Br) = Relative rate of reinforcement (rL/rL+rR)
–but what if two response alternatives (left and right keys here) are not reinforced according to the same schedule
–actually, responses are evenly distributed
–the relative rate of responding to a given alternative is always similar to
–relative rate of reinforcement earned on that alternative
–choice is thus not random, but is an orderly function of rates of reinforcement
-Another major insight derived from matching law
–whether a behavior occurs frequently or not depends not only on its own schedule of reinforcement but also on availability of
alternative sources of reinforcement
What is Undermatching, Overmatching, and Response Bias?
-Most instances where the relative rates of responding do NOT match rates of reinforcement exactly, such apparent flaws in matching law can be accommodated by the generalized form of the matching law
–where b is response bias: occurs when response alternatives require different amounts of effort OR the reinforcer provided for one response is more attractive (either results in preference/bias)
–s is the sensitivity of the choice behavior to relative rates of reinforcement for the response alternatives
–S = 1 for perfect matching
–If s < 1 = undermatching, a common deviation from perfect matching (rL/rR becomes smaller)
-Overmatching: antithesis of undermatching; response ratio/proportion is greater or more extreme than reinforcement ratio/proportion (Bl/Br > rL/rR)
